There are fears one of Wales’ most popular canals could start to dry up within a week, prompting calls for the Welsh government to intervene.

Operators of the 225-year-old Monmouthshire and Brecon Canal have warned of an “urgent” water shortage without the prospect of imminent rainfall.

It comes amid debate over how the historic attraction should secure its water supply in future after limits were placed on taking water from the environmentally-sensitive River Usk.

The Welsh government said any arrangement between the Canal & River Trust and Welsh Water would be a commercial decision in which it should play no role.

The 35-mile (56 km) waterway weaves its way through the Bannau Brycheiniog National Park – formerly known as the Brecon Beacons National Park – and the Blaenavon industrial landscape World Heritage Site, attracting an estimated 3 million visitors a year for boating, walking and cycling.

“Everything the canal supports is at threat – we risk losing the jewel in the crown of south Wales,” said Tracey Leake-Jones, who runs the Bridge 46 to Five Locks canal group.

Made up of volunteers, the group runs events along the canal and has fundraised to install planters, benches and signs.

The prospect of it having to close due to water shortages was “utterly devastating”, she said.

“There has to be a solution found, and my view is that the Welsh government and its leaders are the only people who can bring all the main players together.”

She pointed to new housing estates being built along the canal with the waterway used as a marketing tool, and said the local council hoped to be able to open up further stretches down to Cwmbran, describing the economic benefits as “unimaginable”.

“Should we have problems with water supply then what’s going to happen to those plans for restoration that we’ve all been working on for the past three years?”

News broke of the difficulties facing the canal in a letter sent to local businesses by Glandŵr Cymru, the Canal and River Trust in Wales, in February.

It explained the canal, which once transported iron and coal to Newport docks, had relied on funnelling water from the River Usk and its tributaries which accounted for 80-90% of its water supply.

Recent changes in legislation, designed in part to protect rivers in the face of climate change, means licenses are now required, restricting the amount of water that can be taken.

Last year, Glandŵr Cymru lost an appeal against some of the conditions stipulated by environmental regulator Natural Resources Wales (NRW).

The River Usk is a designated special area of conservation protected by law due to its importance for rare wildlife including the Atlantic salmon, which is threatened with extinction from Wales.

“The canal took around 30% of the total flow of the river in 2022 – which was the last dry year period,” said Gail Davies-Walsh, chief executive of Afonydd Cymru which represents river groups across Wales.

Limits on abstraction were needed to ensure the species and habitats had sufficient water to survive “particularly during dry summers and low flow periods,” she said.

Mark Evans, director of Glandŵr Cymru, said the trust accepted it could no longer continue to abstract water from the Usk at the same level as it had in the past.

But recent dry weather highlighted the urgency of finding an alternative supply, he said.

“The amount of water we can take is starting to really concern us,” he explained.

“It’s urgent today, looking at the forecast for the next week.

“At some point we’ll have to stop the boats from using the locks,” he warned, adding that both the canal’s users and its wildlife would be impacted as levels fell.

Discussions have been taking place in recent weeks with Welsh Water over whether it could help to support the canal during periods of prolonged dry weather.

But this would come with “financial implications” and the potential of having to pay commercial rates for the water, resulting in a considerable bill the charity could not afford, he claimed.

Alasdair Kirkpatrick, owner of Beacon Park Boats, said he had already received phone calls from customers who had booked boat trips asking about the impact on them.

“I never saw this one coming,” he said, “it has really shocked us all.”

“All my customers nip down to the local pubs and restaurants, 25% of them fly in from overseas from places like America and Australia, using local taxis and train services and spending a fortune locally,” he added.

He urged the Welsh government “to fund Welsh Water to continue to maintain water levels and keep all the operators of this canal in business – it cannot be lost”.

Gavin Bown from Natural Resources Wales said regulating water abstraction was “a complex, evidence-based process that carefully balances environmental needs with those of local communities”.

“Our priority is to protect the integrity of the River Usk and the Severn Estuary, both designated as special areas of conservation,” he explained, adding the regulator would continue to work collaboratively with the Canal and River Trust.

A Welsh Water spokesman said the River Usk was “one of the primary sources of drinking water to around 250,000 customers across south east Wales”.

But it remained “one of our least drought resilient supply areas”, with limited water resources to deal with the impacts of climate change and population growth.

“We have proposed in the driest of years to supply some customers with water from the River Tawe through an emergency pumping station and use this spare capacity in abstraction from the River Usk to support the canal,” he explained.

However this would come at a cost, with discussions ongoing over whether this would be affordable to the trust.

“To provide this free of charge or risk the future supply of drinking water to our customers, isn’t an option for us,” he said.

The Welsh government said “protecting and enhancing our environment and natural resources is key to addressing the climate and nature emergencies”.

“The limits placed on the licences were in line with the amounts applied for by the Canal & River Trust,” a spokesperson said.

They added any arrangement between the canal and Welsh Water would be a commercial contractual decision in which the Welsh government should play no role.